Our work is concerned with the elucidation of basic principles in the development of higher organisms. The emphasis is on understanding the processes by which cells become committed, i.e. determined, to a particular developmental pathway and the processes that order various determination in space, i.e. pattern formation. The advantages of applying genetic methodology make Drosophila an organism of choice as a model system for investigating these fundamental processes. We plan to use a temperature-sensitive mutation to study in particular, aspects of tumor growth, cell commitment, embryonic development, and genetic regulation. The results promise to increase our understanding of processes basic to normal development and neoplastic growth.